Supreme Court nominee Brett M. Kavanaugh’s years-old remarks questioning the landmark ruling that forced President Richard M. Nixon to turn over the Watergate tapes opened a new front in the battle over his confirmation, ensuring his views on executive power will square prominently in Senate hearings.

Included in the thousands of pages turned over to the Senate Judiciary Committee this past weekend is a 1999 transcript of a panel discussion in which the future Supreme Court nominee opined whether the “tensions of the time led to an erroneous decision” in the case United States v. Nixon.

Although Kavanaugh has defended the 1974 ruling in other remarks, Democrats have seized on his skepticism from nearly two decades ago to build a key argument against the nominee: That he won’t be a sufficient check on the president who appointed him.

“If Kavanaugh would’ve let Nixon off the hook, what is he willing to do for President Trump?” Senate Minority Leader Charles E. Schumer (D-N.Y.) asked Monday.

Democrats have also focused on Kavanaugh’s rulings in favor of broad presidential power and his criticism of the independent counsel law to suggest that he would protect Trump from special counsel Robert S. Mueller III’s probe. The judge has been outspoken in saying, for instance, that he would “put the final nail in” the now-defunct independent counsel law.

But it is unclear whether Kavanaugh’s dim view of the independent counsel law extends to separate special-counsel regulations governing Mueller’s investigation into Russian interference in the 2016 presidential election. Mueller’s legal battle with Trump’s lawyers over his request to interview the president could end up before the Supreme Court.

On the Nixon decision, Kavanaugh’s allies rallied to his defense. They pointed out that he had praised the unanimous ruling in the case — which forced Nixon to turn over the Watergate tapes and ultimately led to his resignation — in other venues, such as a law review article in 1998 and a speech in 2016.

Former independent counsel Kenneth Starr, for whom Kavanaugh worked during the 1990s probe into President Bill Clinton, and two other deputy counsels issued a statement Monday stressing that they discussed the Nixon case multiple times during their investigation and that Kavanaugh “viewed that decision as one of the most important decisions in Supreme Court history.”

“We repeatedly relied on Nixon in opposing efforts by the Clinton Administration to shield important evidence from disclosure,” said Starr and the deputies, Mark Tuohey and Bob Bittman. “Our clear recollection of Brett’s views on Nixon is that they are entirely consistent with those he expressed in articles published in 1998 (where he wrote that Nixon should be followed by the Supreme Court), in 2014 (where he identified Nixon as one of the ‘most significant cases in which the Judiciary stood up to the President’), and in 2016 (where he called Nixon one of the ‘greatest moments in American judicial history’).”

Senate Republicans on Monday also dismissed Democrats’ efforts to make Kavanaugh’s views of the Nixon case an issue.

But Kavanaugh’s praise for the decision has been called into question by comments suggesting it may have been wrongly decided, which came during a roundtable discussion about government lawyers and attorney-client privilege.

Philip Lacovara, who had argued United States v. Nixon, said in the discussion that Nixon had taken the position that under the Constitution, no one in the executive or judicial branch could challenge his decision to prevent White House information from being released.

“This question is actually very interesting,” Kavanaugh said, noting that Clinton White House lawyers involved in the roundtable discussion had not questioned whether the court’s ruling was correct.

“But maybe Nixon was wrongly decided — heresy though it is to say so,” Kavanaugh said, according to a transcript of the discussion published in the January-February 1999 issue of the Washington Lawyer. “Nixon took away the power of the president to control information in the executive branch by holding that the courts had power and jurisdiction to order the president to disclose information in response to a subpoena sought by a subordinate executive branch official. That was a huge step with implications to this day that most people do not appreciate sufficiently.”

In an interview Monday, Lacovara said Kavanaugh was not being provocative or playing devil’s advocate.

“The idea that Brett was expounding was this very philosophical approach” regarding whether a president must disclose information because a government subordinate seeks it in a federal criminal investigation, he said.

The White House did not respond to questions about the views Kavanaugh expressed in the discussion. His supporters and former clerks have noted he has called United States v. Nixon one of the three “most significant ­cases in which the judiciary stood up to the president.”

“It’s clear that the #Resistance is attempting to distort, distract and deceive to smear a highly qualified nominee,” said Taylor Foy, a spokesman for Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa). “A closer look at the public record shows a far different story than what the left is peddling.”

In a 1998 law review article, Kavanaugh said in a footnote that he assumed the courts would have the authority to weigh in on a special counsel’s motion to enforce a subpoena because the Supreme Court had held so in Nixon “and there is no reason to revisit that decision.”

Democratic senators said they would ask Kavanaugh to discuss the precedent in his confirmation hearing because he discussed it at the panel discussion.

In addition to his comments on the Nixon ruling, Democrats also say Kavanaugh’s past interviews, writings and judicial opinions reveal a philosophy greatly deferential to the chief executive — a view that Schumer has called “almost monarchical.”

“It is revelatory of his beliefs, and they fit a pattern that is deeply disturbing,” Sen. Richard Blumenthal (D-Conn.), a member of the Senate Judiciary Committee, said Monday.

Kavanaugh is continuing to meet privately with senators ahead of his confirmation hearing, which has not been scheduled. He will sit down Tuesday with Sen. Rand Paul (Ky.), his most vocal Republican critic. Although most Democrats had boycotted the courtesy visits with Kavanaugh until a separate impasse over his documents is resolved, Sen. Joe Manchin III (D-W.Va.) will meet with the judge next Monday, a spokesman for the senator said.

But Schumer and Sen. Dianne Feinstein of California, the top Democrat on the Senate Judiciary Committee, had so far refused to sit down with Kavanaugh, demanding access to all paperwork that Kavanaugh touched during his time in the George W. Bush administration. He spent five years in the Bush White House, including serving as staff secretary.

Feinstein said Monday that she and Grassley have hit the “first glitch” over the discussions over Kavanaugh’s documents, but she declined to elaborate.